chore(package): update rsvp to version 4.8.1

Closes #270

Author: greenkeeper[bot]

package.json

@@ -62,7 +62,7 @@
     "loopback": "^3.16.2",
     "loopback-datasource-juggler": "^3.13.0",
     "mocha": "^4.0.1",
-    "rsvp": "4.7.0",
+    "rsvp": "4.8.1",
     "semantic-release": "^12.2.2",
     "standard": "^10.0.3",
     "supertest": "^3.0.0",